East Mesa Geothermal Projects - Units 1,2,3, and 4 - Executive Summary
The East Mesa Geothermal Projects Plant East Mesa (PEM) Units 1, 2, 3, and 4 are operated by FPL Energy Operating Services Inc and located in Holtville, Imperial County, California. The East Mesa Geothermal Projects generate electricity from renewable geothermal resources in an environmentally friendly manner. FPL Energy Operating Services is committed to safe, environmentally sensitive operation of the East Mesa Geothermal Projects facility. The East Mesa Geothermal Projects are operated in compliance with all federal, state, and local environmental and safety regulations. Emergency response coordination procedures are in place with local emergency response agencies. The Process Hazard Analysis completed for the isopentane processes will be reviewed and updated on a regular basis, as required, to continue to ensure that the processes are operated in the safest possible manner. |
Each of the four, physically separate, Plant East Mesa Units represents a covered process under RMP regulat
ions. Isopentane is the flammable substance of interest. The covered process at each unit includes both the storage and use of isopentane. Isopentane is used as the motive fluid in the generation of electricity from natural geothermal fluid, in a series of interconnected Ormat Energy Converter (OEC) machines at each PEM Unit. Geothermal fluid is used to heat isopentane liquid to vapor in the OEC, and in turn the vapor is used as the motive fluid to spin a generator, generating electricity. The isopentane is then condensed and reused in a continuous, closed loop process within each OEC. At each PEM Unit, isopentane is also stored in one or more storage tanks.
The off-site consequence analysis completed for the RMP addresses a worst-case release event that postulates the extremely improbable release of the entire contents of the largest storage tank on site, at PEM Unit 3. We do not believe that such an event could reasonably be expected to occur; however, EPA requires us to ev
aluate this specific worst case event. The level of significance for the worst case event has been established by the EPA to be "the 1 psi overpressure endpoint" - in other words, the area within which the pressure is one pound per square inch greater than normal atmosheric pressure (about 14.7 psi).
The distance to the endpoint of concern for the worst case event is estimated to be 0.3 miles. In other words, the area significantly affected by such a worst case release is limited to a radius less than 1/3 mile from the tank. Within this radius, there are no public receptors of any kind. Therefore, the worst case release event, while extremely improbable, would none-the-less have no impact on the public.
The East Mesa Geothermal Projects are physically located in a relatively remote area, away from residences and publically used properties. The nearest area normally used by the public is the Desert Hot Springs recreation area, located along the southern boundary of the East Me
sa Geothermal Projects facility. This recreation area is almost three miles from the nearest isopentane storage tank on site.